I just bought a 1983 300 SD, 104K on odometer.
I drove it from Taylor, TX to Fredericksburg, TX and back (approx. 200 mi). The engine ran as smoothly as could be imagined until about 8 mi. from my office. At first it was an almost imperceptible missing, which became more pronounced the closer I got to work. About a quarter of a mile before I got there it began to knock or hammer, coming from the engine.
During this process, the battery light came on, but the oil pressure stayed where it had been (30), The water temperature did not rise. There was vacuum enough to close up the sunroof and lock/unlock the doors more than 10 times. No belts/hoses were missing, frayed or leaking.
The previous owner had installed a K&N air filter and taken off the factory model.
On the advice of Roy Hunter, I have DieselPurged, adjusted the valves, changed filters, replaced the aux. fuel pump.
The symptoms: a knocking sound -- loud and a function of engine rpms.
Exhaust, smoky, but doesn't smell like burnt sugar or glycol.
Oil: black like someone put a moly in it, but no signs of water.
Coolant: bright green, no sign of oil.
I am ordering a compression tester to check the cylinders.
Suggestions/comments appreciated -- I don't have enough money to go fixing things that aren't broken.
Thanks,
Paul

Why do you believe the sound was coming from the engine? Have you opened the hood and searched for the sound?

To me it sounds like an alternator bearing failure..........and I'm nowhere near it.

I'm leaning towards a bad vacuum pump. The sunroof is electric and the doors are run by an electric vacuum pump separate from the engine pump.
Do you have a mechanics stethescope you can put on the engine to try to isolate the noise?
Black oil is normal in these engines.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Whatever the cause, it sounds like it is rapidly progressing. As mentioned it could be the vac pump among other things, & at the rate its accelerating, I think I would be inclined to pull that vac pump off & give it a good inspecting on the roller before I run the engine any more. Its easy and quick enough to do, and well worth the peace of mind knowing you arent going to puke it into the timing chain and really have a mess. If it's ok, put it back and try running the engine without the belts installed (not for very long though) to see if the noise disappears. If so, install one at a time until the noise returns.

__________________
Chris
64 190D R.I.P.
80 240D W/617 engine -for sale
82 240D -for sale

My experience with an alt bearing failure is a high pitched screeeetch!
Have not encountered a failing vac pump.
Perhaps an air leak in the fuel system, for the mis, knock. Does the engine rock back and forth?
Good deal with the compression tester, let us know the results. DieselGiant has a write up. If you remove the injectors, be sure to use new crush washers, also known as heat shields, and torque to specs.

__________________
83 SD

84 CD

Paul --

If you need heat shields, let me know. I think I have a small handful left from the NE Texas GTG.

Sunny

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Anthracite 1980 300D -- 64k original miles with a new engine, on the road again!
Silver 300D -- second owner, Sunny's old baby, Ilse, 210 miles,
Having to thin the herd….
Silver 1983 300SD -- second owner, 325k miles
Gold 1981 300D -- well-traveled, solid little car
Beige 1984 300D -- 292k miles, grease machine, parting out
Seafoam green 1981 300SD -- 250k, windshield frame damage
too many assorted w123 & w126 cars, parts cars, and extras

How does the engine run? Do all the suggestions. Check the alternator shaft and the water pump shaft. Bearings can go out and make a huge racket before they finally seize up.

Also, get rid of the green coolant. Use Zerex G-05.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

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91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

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